Streptococcus mutans, etiologic agent of dental caries, is divided into 7 serotypes. We have isolated and characterized antigens possessing determinants for serotypes a, b, c, d and e. Also, we have discovered that rabbit antisera made against many of these strains contain antibodies that bind to human myocardial sections. Cell walls of S. mutans were found to absorb out heart-reactive antibodies from human rheumatic sera. Lipoteichoic acid from these strains did not react with heart-reactive antibodies. These findings dictate caution in the use of anti-cariogenic vaccines and suggest that special oral prophylactic procedures may be required for rheumatics. During the coming period, we plan to isolate and characterize several surface antigens of streptococci that are capable of reacting with human autoantibody. Already we have found that rabbit antisera derived against S. mutans AHT (a), B-13 (d), SL 1 (untyped), S. salivarius 8618 and S. pyogenes 3 RP-26 (rheumatic strain) mutually cross-react in agar immunodiffusion analyses. Three different extraction procedures yield the same cross-reactive antigens, which are not identical with the universal lipoteichoic acid polymers. The discovery of a unique, common antigen found in both viridans ad hemolytic streptococci may affect present modes of antibiotic therapy for rheumatics if this antigen is found to react with human autoantibodies. BIBLIOGRAPHIC REFERENCES: Identification of cariogenic bacteria by fluorescent antibody and other techniques: An international symposium. A. S. Bleiweis (Ed.) J. Dent. Res. 55, Special Issue A (1976). Ultrastructural, physiological and cytochemical characterization of cores in group D streptococci. S.E. Coleman and A.S. Bleiweis. J. Bacteriol. (in press), 1977.